a: \(P=\dfrac{-1+2\sqrt{x}-x+x-2\sqrt{x}+\sqrt{x}+2}{\left(\sqrt{x}-1\right)\left(\sqrt{x}-2\right)}:\dfrac{2x+1-\sqrt{x}}{\sqrt{x}\left(\sqrt{x}-2\right)}\)

\(=\dfrac{\sqrt{x}+1}{\left(\sqrt{x}-1\right)}\cdot\dfrac{\sqrt{x}}{\sqrt{x}+1}=\dfrac{\sqrt{x}}{\sqrt{x}-1}\)

b: Thay \(x=6-2\sqrt{5}\) vào P, ta được:

\(P=\dfrac{\sqrt{5}-1}{\sqrt{5}-2}=3+\sqrt{5}\)

\(\sqrt{x}=y\\ \)

ĐK: \(x\ne0,1,4\Leftrightarrow\left\{\begin{matrix}y>0\\y\ne1\&4\end{matrix}\right.\) ko sửa được y khác 1 &2

\(P=\left(\frac{\left(1-y\right)}{\left(y-2\right)}+\frac{y}{\left(y-1\right)}+\frac{y+2}{\left(y-1\right)\left(y-2\right)}\right):\left(\frac{2}{y-2}-\frac{y-1}{y\left(y-2\right)}\right)\)

\(P=\left(\frac{2y-y^2-1}{\left(y-2\right)\left(y-1\right)}+\frac{y^2-2y}{\left(y-1\right)\left(y-2\right)}+\frac{y+2}{\left(y-1\right)\left(y-2\right)}\right):\left(\frac{2y-y+1}{y\left(y-2\right)}\right)\)

\(P=\left(\frac{y+1}{\left(y-1\right)\left(y-2\right)}\right).\left(\frac{y\left(y-2\right)}{\left(y+1\right)}\right)=\frac{y}{y-1}\)

a) \(P=\frac{\sqrt{x}}{\sqrt{x}-1}\)

b)\(x=6-2\sqrt{5}=5-2\sqrt{5}+1=\left(\sqrt{5}-1\right)^2\)

\(p=\frac{\left(\sqrt{5}-1\right)}{\sqrt{5}-2}=\left(\sqrt{5}-1\right)\left(\sqrt{5}+2\right)=3-\sqrt{5}\)

C)\(\frac{P}{\sqrt{x}}=\frac{1}{\sqrt{x}-1}\ge-1\) tuy nhiên đk: x khác 0=> dấu đẳng thức không xẩy ra (xem lại đề)

Xem lại 1/(căn(x)-1) có cực trị duy nhất khi x=0 tuy nhiên nó cũng không phải GTLN : rất có thể rút gọn P bị sai nếu không đề sai.

a: \(P=\left(\dfrac{2\sqrt{x}}{\left(x+1\right)\left(\sqrt{x}+1\right)}+\dfrac{1}{\sqrt{x}+1}\right):\dfrac{x+1+\sqrt{x}}{x+1}\)

\(=\dfrac{2\sqrt{x}+x+1}{\left(\sqrt{x}+1\right)\left(x+1\right)}\cdot\dfrac{x+1}{x+\sqrt{x}+1}=\dfrac{\sqrt{x}+1}{x+\sqrt{x}+1}\)

b: Thay \(x=9+2\sqrt{7}\) vào P, ta được:

\(P=\dfrac{\sqrt{9+2\sqrt{7}}+1}{9+2\sqrt{7}+\sqrt{9+2\sqrt{7}+1}}\simeq0,25\)

a: \(A=\dfrac{\left(\sqrt{a}-\sqrt{b}\right)^2}{\sqrt{a}-\sqrt{b}}-\dfrac{\sqrt{ab}\left(\sqrt{a}+\sqrt{b}\right)}{\sqrt{ab}}\)

\(=\sqrt{a}-\sqrt{b}-\sqrt{a}-\sqrt{b}=-2\sqrt{b}\)

b: \(B=\dfrac{2\sqrt{x}-x-x-\sqrt{x}-1}{\left(\sqrt{x}-1\right)\left(x+\sqrt{x}+1\right)}\cdot\dfrac{x+\sqrt{x}+1}{x-1}\)

\(=\dfrac{-2x+\sqrt{x}-1}{\sqrt{x}-1}\cdot\dfrac{1}{x-1}\)

c: \(C=\dfrac{x-9-x+3\sqrt{x}}{x-9}:\left(\dfrac{3-\sqrt{x}}{\sqrt{x}-2}+\dfrac{\sqrt{x}-2}{\sqrt{x}+3}+\dfrac{x-9}{x+\sqrt{x}-6}\right)\)

\(=\dfrac{3\left(\sqrt{x}-3\right)}{x-9}:\dfrac{9-x+x-4\sqrt{x}+4+x-9}{\left(\sqrt{x}+3\right)\left(\sqrt{x}-2\right)}\)

\(=\dfrac{3}{\sqrt{x}+3}\cdot\dfrac{\left(\sqrt{x}+3\right)\left(\sqrt{x}-2\right)}{x-4\sqrt{x}+4}\)

\(=\dfrac{3}{\sqrt{x}-2}\)

ĐKXĐ: ....

\(A=\left(\frac{3\sqrt{x}\left(\sqrt{x}-2\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}-\frac{\sqrt{x}\left(\sqrt{x}+2\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}+\frac{8\sqrt{x}}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}\right):\left(\frac{2\left(\sqrt{x}+2\right)-2\sqrt{x}-3}{\sqrt{x}+2}\right)\)

\(=\left(\frac{3x-6\sqrt{x}-x-2\sqrt{x}+8\sqrt{x}}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}\right):\left(\frac{2\sqrt{x}+4-2\sqrt{x}-3}{\sqrt{x}+2}\right)\)

\(=\frac{2x}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}.\frac{\left(\sqrt{x}+2\right)}{1}=\frac{2x}{\sqrt{x}-2}\)

b/ \(A=\frac{2x}{\sqrt{x}-2}=2\sqrt{x}+4+\frac{8}{\sqrt{x}-2}=2\left(\sqrt{x}-2\right)+\frac{8}{\sqrt{x}-2}+8\ge2\sqrt{\frac{16\left(\sqrt{x}-2\right)}{\sqrt{x}-2}}+8=16\)

\(\Rightarrow A_{min}=16\) khi \(\left(\sqrt{x}-2\right)^2=4\Rightarrow x=16\)